
MOLLUSCS, VERMES AND HYDROZOA 

the hinge, which has the margin compressed and considerably curved. 
The surface is smooth, except at the posterior portion, where it is wrinkled 
and shows a number of radiation 



























































FIG. 188. Anaaonta cataracta. Adult. 
The color is a deep clear green, indistinctly radiated with a darker green 
and brown. On the inside the silvery nacre is tinged with blue and yellow 
and has agreenish margin. It reaches a large size and may be 4% inches 
long, 234 inches broad and 1% inch thick, though most of these mussels 
are about 3 inches long. It usually inhabits ponds and still water and 
occurs quite generally on the Eastern Atlantic slope. 
A. implicata, Fig. 189, 1s a characteristic species with transversely 
oblong, sub-oval, thick, opaque, strong and heavy valves, almost as thick 
as broad; having the umbones distinct and usually eroded. It has ridges 
from the lower posterior edge of = 
the umbone to the angular tip 
of the posteriorsedae.) Uhe 
valves are broadest behind the 
middle; the hinge margin is 
slightly curved. ‘The outer sur- 
face is rough with coarse lines of 
growth, of a yellowish-olive color 

somewhat darker above, and the 
lines are marked with a dull brown. Older shells have a delicate salmon 
or flesh-color and the younger a silvery tint on the inside. It grows to 4 
inches long, 214 inches broad and 1% inches thick, but average shells 
are usually about 3 inches long or under. It inhabits ponds and still 
water throughout the Eastern and Middle States but has a quite general 
distribution. This mussel is more elongate, narrower and thicker than 
the foregoing and may be distinguished by its obtuse ridge. The margin 
is also more convex. 
244 
